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Bright tin plates well on aluminum, but not on copper

I have a plating line for tin plating on copper bus bars and I started to see some marks on the plated parts, like gassing marks. The thing is that I'm using the same bath for aluminum tin plate and I don't have the same result on tha aluminum parts, all aluminum are looking very shinny and with an uniform coating. So, I think it could be related to some kind of power trow issue or because after the cleaning process I can't see any stains/marks on the parts. The bad finishing is not only on one side of the part, it is random, you can see the defective area on Low current and also on the High current density areas.

Thanks for your support.

Carlos Alberto Rodriguez Ortiz
Manufacturing Engineer - Juarez, Chihuahua, Mexico
May 8, 2008

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Carlos,
If you are seeing "gassing" marks and assuming the plating solution is within spec., I would clean all contacts (anodic and cathodic) in the copper plating line, clean anodes, and change anode bags. Because copper plating has such high efficiency you should not experience any gassing marks on the parts. You also want to make sure you have adequate bath agitation. Hope this helps you.

Mark Baker
Process Engineer - Syracuse, NY USA
May 12, 2008

I have cleaned all the anode contacts in the tin bath and also have changed the old anode bags for brand new bags, I have an improvement on the amps readings, definitively, but still have a lot of dull copper parts plated, could it be related to a comment I get that it is more difficult to plate bright tin on copper rather than on aluminum? If so, could you explain me how that can happen?

Carlos Rodriguez
- Juarez, Chihuahua, Mexico
May 16, 2008

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Carlos,
I don't think its any harder to achieve bright tin on copper than it is on aluminum. Is your copper pure enough, clean enough and bright enough? Remember the base metal is reflective of the plated part. Tin does not have the same ability of building brightness and hiding blemishes such as a bright nickel does.

Mark Baker
Process Engineer - Syracuse, New York
May 22, 2008